Just watched a video explaining how oil film causes color patterns - first wave is reflected from the outer surface (air-oil), then another wave is reflected from the lower surface (oil-water). Sometimes they strengthen each other, other times they cancel each other - depends on the thickness of the film and the frequency of the wave.
But this means that 2 EM waves interact. Does this mean that photons interact? Or the explanation about waves is purely based on Electrodynamics and from QM perspective this effect is described differently?